Replies to MSN hosted email with Email Workers Don't Work

[syblackwell]

For Workers & Pages, what is the name of the domain?

icendant.chat

What is the error number?

No Cloudflare Error

What is the error message?

Microsoft: could not send email: could not initialize upstream: Unknown error: permanent error (550): 5.7.1 Unfortunately, messages from [104.30.8.91] weren’t sent. Please contact your Internet service provider since part of their network is on our block list (S3150). You can also refer your provider to Troubleshooting. [Name=Protocol Filter Agent][AGT=PFA][MxId=11BB28F001C9D12A] [BN3PEPF0000B077.namprd04.prod.outlook.com 2025-05-19T18:46:12.261Z 08DD947803DEC837]

What is the issue or error you’re encountering

Can’t respond to email from MSN hosted accounts

What steps have you taken to resolve the issue?

Verified all works fine with Google hosted email

Tried 365 Anti-Spam IP Delist Portal. Unfortunately, it appears Cloudflare uses rotating IPS. The portal takes an email address and IP to delist, but when it tries to do the delist as a result of sending an email with a link that I click on (have to use the worker logs to get this link) is says the IP addresses do not match.

Further evidence of rotating IPS is that Microsoft with send slightly different error message at different times, e.g. Unfortunately, messages from [104.30.8.157] vs 104.30.8.91

This is a new domain so I know a bunch of spam has not been sent from it. And, Micosoft is specifically saying it is related to the network and does not mention the domain name.

Certainly the type of thing to resolve before Email Workers come out of beta.

What are the steps to reproduce the issue?

Send email to an email worker from an MSN account.

[GeorgeAppiah]

It seems you’ve switched to Mailgun since posting this. That’s a far superior email solution with SMTP (outgoing) and advanced routing (incoming) capabilities. They also actively police their customers to prevent abuse, leading to a much better deliverability rate.

(These days 99% of messages in my spam box are delivered “via cloudflare-email.net” – so it should be no wonder that major email providers routinely block Cloudflare Email Routing messages.)

If there are still any issues, please let us know in a new topic.

Good luck!

[syblackwell]

Thanks … and even Mailgun did not work aftwr several hours of futzing around. Switched to AhaSend, worked out of the box. One of the easiest setups I have ever done and less expensive than Mailgun for our use case.